The present invention pertains to a method of forming a frame made of synthetic plastic material by molding at least one resilient lip seal of resilient material to a frame of rigid thermoplastic material to form an integral assembly, all operations being done by a single injection molding machine. The present invention is also concerned with a mold cavity for making such a window frame. Alternatively, the present invention is also concerned with a window made of see-through thermoplastic material and provided with an integral peripheral lip seal, and with a method for forming such a window.
Forming window frames using more than one type of plastic material is well known in the art. These window frames are usually provided with a rigid frame portion made of a rigid thermoplastic material and a deformable seal portion made of resilient material.
One method for making such window frames is to separately mold the rigid frame portion and the deformable seal portion and subsequently assemble these two portions mechanically. This method has the significant drawback of requiring post-molding assembly operations that usually increase the production cost of the window frames. Furthermore, since the deformable seal portion is usually made from an extrusion process, the profile of this portion is constant around the periphery of the frame which may be a drawback in some applications.
Another method for making window frames made of more than one type of plastic material consists of a three-step process. First, the frame portion is molded in a first mold assembly. The frame portion is then ejected from the first mold assembly and mounted to a second mold assembly. Finally, the deformable seal portion is molded, in the second mold assembly, directly onto the surface of the frame portion. U.S. Pat. No. 5,503,452 issued on Apr. 2, 1996 to Moretz et al. describes such a method to make a vehicle tilt-out window with seal insert. A major drawback of this technique is that two molds and two injection molding machines are required to form the window frame, resulting in handling and part dimensions problems which affect both the quality and the cost of the product.
It is an object of the present invention to provide an improved method of forming a frame.
It is another object of the present invention to provide a method of molding a frame in a single injection molding machine having multiple identical cores and multiple non-identical cavities.
More specifically, in accordance with the present invention, there is provided a method of forming, in a single injection molding machine having core portion including first and second identical cores provided with movable inserts and a cavity portion including first and second non-identical cavities, a frame of rigid thermoplastic having generally inverted U-shaped cross-section defining a concave portion; the frame also having an integral resilient lip seal and an integral deformable sealing joint provided in the concave portion of the rigid frame, the method comprising the steps of:
molding a frame of rigid thermoplastic material in the first core and in the first cavity defining together a frame configuration having a generally inverted U-shaped cross-section;
opening the mold while maintaining the molded frame in the first core;
moving the core portion so as to bring the first core in line with the second cavity defining a lip seal configuration whereby, simultaneously, bringing the second core in line with the first cavity;
moving the movable insert of the first core so as to open the concave portion of the frame;
closing the mold;
simultaneously a) molding a lip seal by injecting a resilient material over the previously molded frame in the first core and in the second cavity defining a lip seal configuration, b) molding a sealing joint by injecting a deformable material in the concave portion of the frame, and c) molding, in the second core and the first cavity, a second frame of rigid thermoplastic material;
opening the mold
moving the movable insert of the first core so as to close the concave portion of the frame; and
ejecting the first formed frame with lip seal.
According to another aspect of the present invention, there is provided a mold for making a frame of rigid material having a resilient lip seal; the mold comprising:
a core portion provided with at least first and second identical cores;
a cavity portion having at least a) a first cavity configured and sized to mold the rigid material of the frame, and b) a second cavity configured and sized to mold the resilient lip seal; the cavity portion being so mounted to the mold as to be movable in a predetermined direction between a closed position where the cavity portion contacts the core portion and an open position where the cavity portion does not contact the core portion; the second cavity including:
a body;
an internal stripper ring so mounted to the body as to be
movable in the predetermined direction;
an external stripper ring so mounted to the body as to be
movable in the predetermined direction; whereby movements of the internal and external stripper ring in the predetermined direction allow the resilient lip seal to be removed from the second cavity.
According to a third aspect of the present invention, there is provided a mold for making a frame of rigid material having a resilient lip seal; the mold comprising:
a core portion provided with at least first and second identical cores;
a cavity portion having at least a) a first cavity configured and sized to mold the rigid material of the frame, and b) a second cavity configured and sized to mold the resilient lip seal; the second cavity including:
a body provided with at least two first threaded apertures and at least two second threaded apertures;
an internal stripper ring provided with at least two shouldered apertures corresponding to the at least two first threaded apertures of the body;
at least two first compression springs mounted in the first shouldered apertures;
at least two first fastener; each the first fastener being engaged in one of the at least two first threaded apertures of the body through both one of the at least two first compression spring and one of the at least two first shouldered apertures;
an external stripper ring provided with at least two shouldered apertures corresponding to the at least two second threaded apertures of the body;
at least two second compression springs mounted in the second shouldered apertures;
at least two second fasteners; each the second fastener being engaged in one of the threaded apertures of the body through both one of the second compression spring and one of the second shouldered aperture;
whereby the internal and external stripper rings are so mounted to the body through the fasteners and the compression springs that both the internal and external stripper rings may move independently with respect to the body to thereby allow the resilient lip seal to be removed from the second cavity.
According to yet another aspect of the present invention, there is provided a window made of plastic material, the window comprising:
a generally rectangular body made of a see-through plastic material; the generally rectangular body including a generally thick peripheral portion; and
an resilient lip seal mounted to the generally thick peripheral portion of the body.
Finally, according to another aspect of the present invention, there is provided a method of forming, in a single injection molding machine having core portion including first and second identical cores and a cavity portion including first and second non-identical cavities, a window of see-through rigid thermoplastic material having an integral resilient lip seal, the method comprising:
molding a window of see-through rigid thermoplastic material in the first core and in the first cavity defining a window configuration;
opening the mold while maintaining the molded window in the first core;
moving the core portion so as to bring the first core in line with the second cavity defining a lip seal configuration whereby, simultaneously, bringing the second core without a frame in line with the first cavity;
closing the mold;
molding a lip seal by injecting a resilient material over the previously molded window in the first core and in the second cavity defining a lip seal configuration, while simultaneously molding, in the second core and the first cavity, a second window of see-through rigid thermoplastic material;
opening the mold and ejecting the first formed window with integral lip seal.